<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="outer">
        <label>
          <input type="checkbox" />两周内自动登陆
        </label>
        <div id="tips">为了您的安全，请不要打开</div>
      </div>
</body>
</html>
<script>
    window.onload = function() {
  var oTips = document.getElementById("tips");
  var oLabel = document.getElementsByTagName("label")[0];
  oLabel.onmouseover = function() {
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  };
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<style>
    body,
    input,
    p {
      margin: 0;
      padding: 0;
    }
    body {
      font: 12px/1.5 Tahoma;
    }
    #outer {
      width: 200px;
      margin: 10px auto;
    }
    input {
      margin-right: 5px;
      vertical-align: middle;
    }
    #tips {
      padding: 5px;
      margin-top: 5px;
      background: #ffefa4;
      border: 1px solid #f90;
      display: none;
    }
    </style>